Polyurethane foams made with polyols consisting entirely of poly(propylene oxide) units can have superior performance with respect to some physical properties, such as flame retardance. However, these foams are inherently more difficult to process, having narrow processing windows that result in foams having a more closed cellular structure than desired.
Attempts have been made to make polyols from vegetable or renewable feedstocks such as those disclosed by Peerman et al. in U.S. Pat. No. 4,423,162. Peerman et al. describe hydroformylating and reducing esters of fatty acids obtained from vegetable oils, and forming esters of the resulting hydroxylated materials with a polyol or polyamine. The formation of polyurethane foams from natural oil-based polyols is described in U.S. Pat. Appl. Pub. No. 2006/0293400 and in PCT Appl. No. WO 2008/144224. However, none of these references describes a polyurethane foam formed from polyols consisting entirely of poly(propylene oxide) units and having a highly open cell structure, as measured by air flow rates through the foam. Instead, the examples in these references report foams made from ethylene oxide unit-containing polyols, which are not plagued by narrow processing windows in the same way as polyols consisting entirely of poly(propylene oxide) units.